1. Field of the Invention
The present invention relates to photographic film supports and, particularly, to photographic film supports wherein halation and light piping are prevented.
2. Description of the Prior Art
Generally, in supports for motion picture or recording films, halation and "light piping" (or "edge fogging") should be prevented. If such is not prevented, disadvantages occur. For example, when one frame in the film is exposed to light using a camera, (1) incident light scatters in the support or at the interface between the support and a subbing layer to cause formation of dim images due to the undesired exposure of the emulsion in that frame, and (2) incident light passes through the support and reaches another exposed or unexposed frame and the emulsion of the other frame is fogged.
In the past, photographic supports have been dyed to prevent halation and light piping.
For example, it is known that photographic supports can be dyed using red and green dyes, as described in Japanese Patent Application (OPI) Nos. 14245/72 and 5425/73 (The term "OPI" as used herein refers to a "published unexamined Japanese patent application"), and U.S. Pat. Nos. 2,622,026, 3,728,124 and 3,822,132. Further, photographic supports in which finely divided particles of pigments, such as carbon black or titanium oxide, have been incorporated are described in U.S. Pat. No. 3,340,062.
Light by which halation and light piping are caused is visible light, such as sunlight, etc. Accordingly, it would appear that halation and light piping can be prevented, if the photographic film supports were dyed to have an absorption over the entire spectral wavelength range of visible light. Thus, photographic film supports dyed to have a uniform absorption in the entire visible light wavelength range of about 400 to 700 nm are described in U.S. Pat. No. 2,622,026, column 1, lines 16 to 20.
Where photographic film supports are dyed using a mixture of a red dye and a green dye to prevent halation or light piping, there is the disadvantage that prevention of halation or light piping cannot be sufficiently obtained or the apparent sensitivity of the photographic emulsion decreases. Green dyes have main absorption peaks in the wavelength ranges of 400 to 500 nm and 600 to 700 nm. The main absorption peaks in these two wavelength ranges result in an optical density which is generally not the same, namely, the main absorption peak in one range results in an optical density which is higher than the optical density resulting from the main absorption peak in the other range. Therefore, the same optical densities in the wavelength range of 400 to 500 nm and the wavelength range of 600 to 700 nm are not obtained. Accordingly, sufficient prevention of halation and light piping is not obtained in the wavelength range having the lower optical density. Further, although sufficient prevention of halation or light piping can be attained by increasing the concentration of the green dye, if the concentration of the green dye is increased, incident light of the wavelength range having the higher optical density is absorbed by the support to cause the apparent sensitivity of the emulsion sensitized to this wavelength range to decrease.
Further, the method of incorporating finely divided particles of pigments, such as titanium oxide or carbon black etc., has the disadvantage that uniform dispersion of these pigments in the polymers of the support is difficult to achieve and the photographic film support becomes hazy (cloudy) and distinct images cannot be obtained.
By using three kinds of dyes comprising a yellow dye, a red dye and a blue dye and by selecting the mixing ratio thereof, photographic film supports in which the optical densities of each of the main absorption peaks in the wavelength ranges of 400 to 500 nm, 500 to 600 nm and 600 to 700 nm is the same can be obtained, by which deterioration of the sensitivity of the photographic light-sensitive material is minimized and sufficient prevention of halation and light piping can be obtained. Further, in color photographic emulsions having a poor color balance, it is possible to correct the color balance by changing the mixing ratio of the three kinds of dyes.
Dyes for dyeing polyester films for photographic film supports simultaneously must be heat resistant, compatible and sublimation resistant, must be inert to silver halide emulsions and must not adversely influence photographic properties, such as sensitivity, gamma or fog, etc.
Red and blue dyes for polyester films which satisfy these requirements are described in Japanese Patent Application (OPI) Nos. 14245/72 and 5425/73, Japanese Patent Publication Nos. 8734/72, 8735/72 and 33724/76 and U.S. Pat. Nos. 3,728,124, 3,822,132 and 3,933,502. However, no yellow dyes which satisfy the above-described requirements for polyester films are known, and it has been desired to provide yellow dyes which are heat resistant, compatible with polyesters and sublimation resistant, are inert to silver halide emulsions, do not adversely influence photographic properties, such as sensitivity, gamma or fog, etc., and have an absorption in the short wavelength side of the yellow absorption wavelength range of 400 to 500 nm.